Cones are spaced 50 feet apart where
Caltrans workers are "tapering" to shut of a lane, and
100 feet apart at the closed lane. That marks the work
site and discourages people from trying to drive into
the closed lane, which can result in tragic consequences.
The fact that cones appear to be just a few feet apart
helps illustrate that things move fast at freeway speeds
-- another good reason to slow down in a work zone.